From 71a989707eb353977b58deca6080c1a8837c204f Mon Sep 17 00:00:00 2001
From: Misa <infoteddyatgitgud@cock.li>
Date: Thu, 9 Jul 2020 02:54:23 -0700
Subject: [PATCH] De-duplicate and add safety check to ed.level reference

Instead of repeating 'ed.level[curlevel]' (or even worse, you type in
that giant expression inside the brackets instead of reusing
'curlevel'), why not just type 'room'? As an added bonus, I added bounds
checks so 'room' is always guaranteed to point to an existing object.

There are some levels that index 'ed.level' out of bounds, and I'd like
to make their behavior properly defined instead of being undefined. One
of the things usually true about out-of-bounds rooms is that they're
always tiles2.png (that means an edlevelclass tileset that isn't 0),
because the chance of the memory location being exactly 0 is smaller
than it being nonzero. So the out-of-bounds room has tileset 1.
---
 desktop_version/src/Map.cpp | 52 +++++++++++++++++++++++--------------
 1 file changed, 33 insertions(+), 19 deletions(-)

diff --git a/desktop_version/src/Map.cpp b/desktop_version/src/Map.cpp
index 1e04db63..4c04adb2 100644
--- a/desktop_version/src/Map.cpp
+++ b/desktop_version/src/Map.cpp
@@ -1611,10 +1611,23 @@ void mapclass::loadlevel(int rx, int ry)
 #endif
 #if !defined(NO_CUSTOM_LEVELS)
 	case 12: //Custom level
-		int curlevel=(rx-100)+((ry-100)*ed.maxwidth);
+		const int curlevel = rx-100 + (ry-100) * ed.maxwidth;
+		const edlevelclass* room_ptr = NULL;
+		if (!INBOUNDS_ARR(curlevel, ed.level))
+		{
+			static edlevelclass blank;
+			blank.tileset = 1;
+			room_ptr = &blank;
+		}
+		else
+		{
+			room_ptr = &ed.level[curlevel];
+		}
+		const edlevelclass& room = *room_ptr;
+
 		game.customcol=ed.getlevelcol(curlevel)+1;
 		obj.customplatformtile=game.customcol*12;
-		switch(ed.level[curlevel].tileset){
+		switch(room.tileset){
 			case 0: //Space Station
 			tileset = 0;
 			background = 1;
@@ -1626,7 +1639,7 @@ void mapclass::loadlevel(int rx, int ry)
 			case 2: //Lab
 			tileset = 1;
 			background = 2;
-			graphics.rcol = ed.level[curlevel].tilecol;
+			graphics.rcol = room.tilecol;
 			break;
 			case 3: //Warp Zone/intermission
 			tileset = 1;
@@ -1647,16 +1660,16 @@ void mapclass::loadlevel(int rx, int ry)
 		if(redrawbg){
 			graphics.backgrounddrawn = false;
 		}
-		if(ed.level[curlevel].warpdir>0){
-			if(ed.level[curlevel].warpdir==1){
+		if(room.warpdir>0){
+			if(room.warpdir==1){
 			warpx=true;
 			background=3;
 			graphics.rcol = ed.getwarpbackground(rx-100,ry-100);
-			}else if(ed.level[curlevel].warpdir==2){
+			}else if(room.warpdir==2){
 			warpy=true;
 			background=4;
 			graphics.rcol = ed.getwarpbackground(rx-100,ry-100);
-			}else if(ed.level[curlevel].warpdir==3){
+			}else if(room.warpdir==3){
 			warpx=true; warpy=true;
 			background = 5;
 			graphics.rcol = ed.getwarpbackground(rx-100,ry-100);
@@ -1664,8 +1677,8 @@ void mapclass::loadlevel(int rx, int ry)
 		}
 
 		roomname="";
-		if(ed.level[curlevel].roomname!=""){
-			roomname=ed.level[curlevel].roomname;
+		if(room.roomname!=""){
+			roomname=room.roomname;
 		}
 		extrarow = 1;
 		const int* tmap = ed.loadlevel(rx, ry);
@@ -1689,34 +1702,35 @@ void mapclass::loadlevel(int rx, int ry)
 			}
 			const int ex = (ent.x % 40) * 8;
 			const int ey = (ent.y % 30) * 8;
+
 			switch(ent.t){
 			case 1: //Enemies
 				int bx1, by1, bx2, by2;
-				bx1=ed.level[rx-100+((ry-100)*ed.maxwidth)].enemyx1;
-				by1=ed.level[rx-100+((ry-100)*ed.maxwidth)].enemyy1;
-				bx2=ed.level[rx-100+((ry-100)*ed.maxwidth)].enemyx2;
-				by2=ed.level[rx-100+((ry-100)*ed.maxwidth)].enemyy2;
+				bx1=room.enemyx1;
+				by1=room.enemyy1;
+				bx2=room.enemyx2;
+				by2=room.enemyy2;
 
 				if(warpx){ if(bx1==0 && bx2==320){ bx1=-100; bx2=420; } }
 				if(warpy){ if(by1==0 && by2==240){ by1=-100; by2=340; } }
 
-				obj.customenemy=ed.level[tsx+((ed.maxwidth)*tsy)].enemytype;
+				obj.customenemy=room.enemytype;
 				obj.createentity(ex, ey, 56,
 				ent.p1, 4, bx1, by1, bx2, by2);
 				break;
 			case 2: //Platforms and Threadmills
 				if(ent.p1<=4){
 					int bx1, by1, bx2, by2;
-					bx1=ed.level[rx-100+((ry-100)*ed.maxwidth)].platx1;
-					by1=ed.level[rx-100+((ry-100)*ed.maxwidth)].platy1;
-					bx2=ed.level[rx-100+((ry-100)*ed.maxwidth)].platx2;
-					by2=ed.level[rx-100+((ry-100)*ed.maxwidth)].platy2;
+					bx1=room.platx1;
+					by1=room.platy1;
+					bx2=room.platx2;
+					by2=room.platy2;
 
 					if(warpx){ if(bx1==0 && bx2==320){ bx1=-100; bx2=420; } }
 					if(warpy){ if(by1==0 && by2==240){ by1=-100; by2=340; } }
 
 					obj.createentity(ex, ey, 2,
-					ent.p1, ed.level[rx-100+((ry-100)*ed.mapwidth)].platv, bx1, by1, bx2, by2);
+					ent.p1, room.platv, bx1, by1, bx2, by2);
 				}else if(ent.p1 >= 5 && ent.p1 <= 8){ //Threadmill
 					obj.createentity(ex, ey, 2,
 					ent.p1 + 3, 4);